D. Comparatives

If x or y is a finite floating-point or complex number,
the comparison x=y is treated like the everyday use of
equality (that is, with a reasonable relative tolerance),
yielding 1 if the difference x-y falls relatively
close to zero. Tolerant comparison also applies to other relations
and to floor and ceiling (<. and >.);
a precise definition is given in Part III under
Equal (=). An arbitrary tolerance t
can be specified by using the fit conjunction (!.),
as in x =!.t y . The global tolerance can be
queried and set using 9!:18
and 9!:19 .